Diagnostic overshadowing: An evolutionary concept analysis on the misattribution of physical symptoms to pre‐existing psychological illnesses

ABSTRACT This evolutionary concept analysis explores the meaning of diagnostic overshadowing within the context of physical health care for individuals with mental illness. Diagnostic overshadowing, the misattribution of symptoms of one illness to an already diagnosed comorbidity, leads to compromised patient care and likely contributes to increased mortality experienced by individuals with mental illness. A systematic literature search led to identification of a sample of 25 publications on the topic. Following Rodgers' Evolutionary Concept Analysis methodology, this literature sample yielded unifying definitions, shared themes, factors contributing to the action of diagnostic overshadowing, outcomes caused by this type of misdiagnosis, and possible interventions available to nurses and other healthcare providers. Understanding of the concept diagnostic overshadowing may help prevent its occurrence and its adverse results.


INTRODUCTION Background
The Institute for Health Metrics and Evaluation (IHME) indicates 13% of the world's population has a mental illness (2019). This large population bears heavy physical as well as psychological burdens. Individuals with mental illnesses die an average of 10 years sooner than their neurotypical peers, with more than 67% of deaths attributed to heart disease and cancer (Walker et al. 2015). Depending upon mental illness and geographic location, decreases in average life span can exceed 20 years (Laursen et al. 2013;Stefancic et al. 2021). Such disparities extend across psychiatric diagnoses and are not limited to specific categories or levels of illness (Lawrence et al. 2010).
Diagnostic overshadowing presents one possible factor behind this inequity (Happell et al. 2016;Ho et al. 2021). The Encyclopedia of Autism Spectrum Disorders defines the term 'diagnostic overshadowing' as a 'negative bias impacting a clinician's judgment regarding co-occurring disorders in individuals who have intellectual disabilities or other mental illness' (Kanne 2013). While not commonly listed with cognitive and clinical biases (Centre for Evidence-Based Medicine 2021; Croskerry 2015Croskerry , 2019, recognition continues to grow for this phenomenon as a type of bias within health care (Becker-Haimes et al. 2021;Hinde et al. 2021;Jamieson & Mason 2019). Knowledge of diagnostic overshadowing is particularly vital for nurses as they are not only hands-on care providers but lead advocates for patient care (Chuttoo & Chuttoo 2019;Mart ınez-Mart ınez et al. 2021).
Concept analysis provides a useful tool for understanding the causes, meanings, and consequences of diagnostic overshadowing. Pioneered within nursing, concept analysis applies an 'approach by which concepts that are of interest to a discipline are examined in order to clarify their characteristics or attributes' (Cronin et al. 2010, p. 62). This paper offers an evolutionary concept analysis of diagnostic overshadowing applied within the context of physical illness misattributed to mental illness.
Beth Rodgers, formulator of the evolutionary concept analysis process used in this paper, discourages repeated analyses of the same concept (2018). Supporting the distinctive nature of this review, extensive searching of English language literature yielded no other published concept analysis on the topic. While the phenomenon of diagnostic overshadowing has been the subject of a meta-analysis (White et al. 1995) and a qualitative systematic review (Molloy et al. 2021a), neither provides the in-depth exploration of term meanings and implications afforded through concept analysis methodology. Rodgers' (1989Rodgers' ( , 2000 evolutionary view of concept analysis encourages inquiry into how disciplines or cultures employ a concept over time. Rodgers' technique, built on the work of Wilson (1963) and Walker and Avant (1988), involves the conduct of primary activities that may take place simultaneously or out of sequence. These activities incorporate: identification of a concept, related terms, and appropriate settings and populations for exploration; data collection and analysis; exemplar presentation; and interpretation of findings, including what those findings might mean for future development of the idea (Rodgers 2000). To ensure adherence to current application of this methodology, a recent evolutionary analysis co-authored by Rodgers (Pinto et al. 2017) has been consulted in concert with the original guidance (Rodgers 1989(Rodgers , 2000. separately for in-process materials not yet appearing in EBSCOhost's MEDLINE. Google Scholar was also searched. Searching resources from multiple areas of knowledge enables greater understanding of the concept's usage across professions (Harari et al. 2020). This broad view is useful, particularly due to the diverse settings in which nurses work and the varied disciplines that impact individuals affected by mental and physical illnesses.

Date range
A starting publication date of 2007 was selected in setting a timeline for articles included in the formal analysis. This date follows the late 2006 release of a report by the United Kingdom's Disability Rights Commission. This report (Disability Rights Commission 2006) is noted within a Joanna Briggs Institute (JBI) research protocol (Molloy et al. 2021b) and its resulting qualitative systematic review (Molloy et al. 2021a) focused on diagnostic overshadowing in a mental health context. This Disability Rights Commission report bridges usages of the term and states, 'both people with learning disabilities and people with mental health problems experience 'diagnostic overshadowing', that is reports of physical ill health being viewed as part of the mental health problem or learning disabilityand so not investigated or treated ' (2006, p. 6). As concept analysis methodology focuses on a concept's usage over time (Rodgers 2000), this analysis examines development of the concept within the Disability Rights Commission report and in materials published thereafter. Older publications are referenced to provide valuable historical perspective.

Additional criteria
To better focus the analysis, criteria in addition to publication date restrictions were set for inclusion of materials to be analysed. As the author's primary reading language is English, only English language publications were considered. Selected publications must also use the exact phrase 'diagnostic overshadowing' and provide a distinct definition for the term. Departing from the Disability Rights Commission's (2006) inclusion of both intellectual disabilities and mental health illnesses and in alignment with the more recent JBI research protocol (Molloy et al. 2021b), this analysis focuses on diagnostic overshadowing in this context as the mistaken diagnosis of physical ailments as emanating from pre-existing psychological illness. The JBI protocol states misdiagnosis of symptoms of mental illness in individuals with intellectual disabilities as arising from their intellectual disabilities is a 'different phenomenon' (Molloy et al. 2021b(Molloy et al. , p. 1364) from misdiagnosis of symptoms of physical illness as emerging from psychiatric disorder. This exclusion is not intended to diminish diagnostic error involving intellectual disability and mental illness as a valid type of diagnostic overshadowing. Rather, application of this exclusion criteria acknowledges misdiagnosis of physical illness as psychiatric in cause constitutes a distinctive manifestation of the phenomenon.

Searching
Literature searches for the phrase 'diagnostic overshadowing' were primarily conducted in late September 2021 with follow up searches occurring in November and December 2021 and early January 2022. Search strategies were informed by guidance from Preferred Reporting Items for Systematic Reviews and Meta-Analyses' (PRISMA) searching extension document (Rethlefsen et al. 2021). Searches of the noted databases carried out in late September 2021 indicated 396 academic and professional articles, reports, and indexed book chapters might meet inclusion criteria. In-process searching of the PUBMED-MEDLINE interface did not yield additional relevant materials. In addition, limited Google Scholar searching (review of the first 150 results) including professional and scholarly journal articles, conference presentations, graduate student publications, technical reports, and academic book publications failed to detect relevant materials not already identified in prior searches.
All results were reviewed at the title and, where warranted, abstract level (Mateen et al. 2013). Of these, 32 publications appeared relevant for full text review. Follow up searches yielded an additional 4 resources needing full text review. The full text of these 36 (total) publications was reviewed and 25 were found to meet inclusion criteria. References for these 25 publications were then reviewed to detect additional applicable materials. The author did not find additional relevant publications not already identified during prior searches. A scaled down reporting of results is provided ( Fig. 1) and additional search information is available upon request.
Articles published within peer-reviewed journal make up the bulk of publications selected for analysis. The 2006 Disability Rights Commission is a notable exception. The Disability Rights Commission, now subsumed within the Equality and Human Rights Commission, was a major force in human rights advocacy in the UK. As the Equity and Human Rights Commission, has received high recognition as a human rights organization from the United Nations (Equality and Human Rights Commission 2020). In addition, though the analysed article by Thornicroft et al. (2007) was published in the peer-reviewed journal International Review of Psychiatry, it is excerpted from a 2006 book by Thornicroft.

Usage
'Diagnostic overshadowing' appears in English language research literature in the early 1980's to describe the misattribution of psychological issues to comorbid intellectual disabilities (Reiss et al. 1982). Usage morphs a quarter century later as the term is applied to the faulty attribution of physical symptoms from somatic illness to psychosomatic origins (Merrick & Merrick 2007;Thornicroft et al. 2007). The term has since evolved to encompass misattribution of one undiagnosed mental illness to an already diagnosed, comorbid mental illness (

Related concepts
Several other concepts connect with the diagnostic overshadowing. In health care, biases related to the concept of diagnostic overshadowing include anchoring, premature closure, and implicit biases (Croskerry 2019;Joint Commission 2016;Saposnik et al. 2016;Tsipursky 2020). Anchoring bias describes reliance upon initial impressions even after receiving additional, deviating information (Joint Commission 2016). Similarly, premature closure bias entails ceasing investigation after the formulation of an initial diagnosis (Croskerry 2019). Implicit bias involves preconceptions of race, ethnicity, gender, diagnoses, etc. and their effects on patient interaction and care (Blair et al. 2011;Tsipursky 2020). Such reflexive reactions may lead to missed diagnoses, ineffective therapies, and disrespectful interactions; these outcomes relate to diagnostic overshadowing as well (Joy et al. 2016;Stoklosa et al. 2017).
Terms related to diagnostic overshadowing also focus on incorrect perceptions inherent to the concept.
These terms include 'misdiagnosis' and 'missed diagnosis', 'diagnostic error', and 'medical error' (Cho 2019;Jones et al. 2008;Molloy et al. 2021b Clarke et al. (2007) and Thornicroft et al. (2007) (Jones et al. 2008;Shefer et al. 2014Shefer et al. , 2015van Nieuwenhuizen et al. 2013) as well as the editorial. Whether reliance on the editorial's definition arises from ease or expertise, the description of diagnostic overshadowing it provides is succinct and most summations in the sample do not notably deviate.

Themes
Unifying themes (Table 1) Table 1 offers an overview of conditions, definitions, and thematic elements present within the sample.

Antecedents
In concept analysis, factors that contribute to the actions a concept describes are called antecedents (Table 2). Providers' bias toward believing that difficult-to-diagnose physical symptoms in individuals with mental illness are psychosomatic in nature (Jones et al. 2008;Joy et al. 2016;Molloy et al. 2021a,b;Nash 2013;Shefer et al. 2014Shefer et al. , 2015Thornicroft et al. 2007) presents a primary antecedent. The misgivings of individuals with mental illness over whether

Consequences
The literature sample also highlights consequences brought about by diagnostic overshadowing (

DISCUSSION
Diagnostic overshadowing as a concept encompasses multiple complicated issues: need, misunderstanding, fear, prejudice, intention, and suffering. While the phrase invites images of a diagnosis obscuring others with its bulk, the stigma attached to mental illness is itself the concealing mass (Ho et al. 2021;Perrone McIntosh 2021;Shefer et al. 2014;van Nieuwenhuizen et al. 2013). As a term, diagnostic overshadowing relies more upon metaphor than accuracy. Mental illnesses often receive a good deal of metaphorical overlay as well. In Illness as Metaphor (1978), American writer and activist Susan Sontag posits, '.. illness is not a metaphor, and that the most truthful way of regarding illnessand the healthiest way of being illis one most purified of, most resistant to, metaphoric thinking' (p. 3). The illnesses obscured by the action of diagnostic overshadowing are frequently more harmful than the mental illness blamed for disguising them. By allowing perceptions of a patient's mental illness to diminish other aspects of their health, practitioners lose valuable opportunities to help these patients avoid dire outcomes.
How might nurses and other providers prevent diagnostic overshadowing from occurring? Whether an answer is engaging in self-critical evaluation (Wood & Tracey 2009) or receiving education on traumainformed care (Stoklosa et al. 2017), collaboration between physical and mental healthcare professionals (Shefer et al. 2015;van Nieuwenhuizen et al. 2013), changes in charting practices (Joy et al. 2016), or, likely, a mixture of these intervention approaches, one critical initial move must be made. This first step requires acknowledging that diagnostic overshadowing exists and that its occurrence is both widespread and serious (Giddings 2013;Happell et al. 2016).

CONCLUSION
As a concept, diagnostic overshadowing began as a way of naming the issue of missed diagnoses of mental illnesses in individuals having intellectual disabilities. The term then took on the meaning of physical illness misattributed to comorbid mental illness. The term now appears in descriptions of the misdiagnosis of one physical malady as being caused by a different, already diagnosed physical illness (Agaronnik et al. 2021;Barnett et al. 2021;Chhugani et al. 2021;Iezzoni 2019). Further developments may occur if diagnostic overshadowing achieves wider recognition within the realm  Molloy et al. 2021a,b).
Additional evolution of this concept may even render it applicable to any misattribution of symptoms to a pre-existing diagnosis. The term is likely broad enough to encompass all such meanings, and literature suggests limited usage of this interpretation is already underway (Osborne et al. 2017). No matter the type of illness, reducing or eliminating misdiagnosis is crucial. When practitioners manage preconceptions of patients with mental illness and actively work with them to address modifiable risk factors (smoking, diet, physical activity), mortality differences greatly diminish (Dregan et al. 2020). If lessening diagnostic overshadowing for all patients yields similar benefit, then sharing the terminology is worthwhile.
Nurses continue to labour as primary providers of, and primary advocates for, patient care. These roles offer sufficient challenge without the seeming obstacle of a patient's mental illness. However, by understanding and recognizing diagnostic overshadowing, nurses can better fulfil these roles as providers and advocates. In the process, this knowledge may assist them in educating colleagues and improving both the quantity and the quality of patients' lives.

RELEVANCE TO CLINICAL PRACTICE
Nursing theory and nursing practice are inextricably linked. Concept analysis provides one such important linkage. By acquiring nuanced knowledge of a concept and its meanings, connections, implications, and future directions, nurses may more expertly handle complications and opportunities presented by the issue. In the case of diagnostic overshadowing, such understanding should lead to recognizing and preventing its occurrence, improving patient-provider relationships, and preventing unnecessary loss of life.

FUNDING INFORMATION
No funding was received for the commission of this research.

DATA AVAILABILITY STATEMENT
Data sharing not applicable to this article as no datasets were generated or analysed during the current study.